Process for producing a coated packaging material and packaging material having at least one barrier layer for hydrophobic compounds

Abstract

The invention relates to a method for producing a coated packaging material, in which at least the steps of a) providing a substrate having a base material of cellulose, an outer side to be faced away from the packaging item as well as an inner side to be faced towards the packaging item, b) coating at least the inner side of the substrate with at least one layer of an aqueous composition, which includes at least polyvinyl alcohol and/or at least one polyvinyl alcohol copolymer as well as a cross-linking agent.

The invention claimed is: 
     
       1. A method for producing a coated packaging material, comprising at least the steps of:
 a) providing a substrate, which has a base material of pulp, an outer side to be faced away from the packaging item as well as an inner side to be faced towards the packaging item, wherein the base material is coated or uncoated paper, coated or uncoated cardboard, or coated or uncoated paperboard; 
 b) coating at least the inner side of the substrate with at least one layer of an aqueous composition including at least polyvinyl alcohol and/or at least one polyvinyl alcohol copolymer as well as a cross-linking agent, wherein the aqueous composition has at most 40% by wt. of polyvinyl alcohol and/or polyvinyl alcohol copolymer and a total solid content of at most 55% by wt., wherein as cross-linking agent at least one alkyl orthosilicate and/or at least one bi-, tri-, or multi-functional compound, which can react with the hydroxyl groups of the polyvinyl alcohol and comprises at least two functional groups selected from carbon acid and acid anhydride, is used, and wherein a pH value of the aqueous composition is adjusted to a value between 1 and 6.5 before application to the substrate; and 
 c) drying the layer and cross-linking the polyvinyl alcohol and/or the polyvinyl alcohol copolymer with the aid of the cross-linking agent with formation of a barrier layer for hydrophobic compounds, wherein the cross-linking agent contributes to the formation of a three-dimensional network by reaction with said polyvinyl alcohol and/or said polyvinyl alcohol copolymer. 
 
     
     
       2. The method according to  claim 1 , wherein an aqueous composition
 with a content of polyvinyl alcohol and/or polyvinyl alcohol copolymer between 2% by wt. and 35% by wt.; and/or 
 with a total solid content between 2% by wt. and 52% by wt.; and/or 
 with a water content of at least 45% by wt. is used. 
 
     
     
       3. The method according to  claim 1 , wherein polyvinyl alcohol and/or a polyvinyl alcohol copolymer with:
 a degree of hydrolysis between 75% and 100%; and/or 
 a degree of polymerization between 100 and 3000; and/or 
 with an average molecular weight between 11000 g/mol and 60000 g/mol 
 
       is used. 
     
     
       4. The method according to  claim 1 , wherein an aqueous composition is used, which includes at least one further polymer and/or copolymer as an additive. 
     
     
       5. The method according to  claim 4 , wherein the at least one further polymer and/or copolymer is dispersed in the aqueous composition and/or that the at least one further polymer and/or copolymer is selected from a group including poly(meth)acrylates, polymethyl(meth)acrylates, polyamides, biopolymers, chitosan, polyurethanes, polyvinylacrylates, polyesters, poly(meth)acrylic acid esters, polyvinylesters, polylactic acid esters, polyhydroxyalkanoates, polyhydroxybutyrate and/or polyhydroxybutyric acid and/or copolymers hereof. 
     
     
       6. The method according to  claim 1 , wherein as the cross-linking agent one or more of tetraethylorthosilicate, malonic acid, glutaric acid, adipic acid, citric acid, butanetetracarboxylic acid and maleic acid is used. 
     
     
       7. The method according to  claim 1 , wherein an aqueous composition is used, which includes between 0.01 and 55 portions of weight of cross-linking agent and/or between 1 and 60 portions of weight of a filler and/or a pigment related to 100 portions of weight of polyvinyl alcohol and/or polyvinyl alcohol copolymer. 
     
     
       8. The method according to  claim 7 , wherein a filler and/or a pigment is used, which is acid-stable and/or has at least substantially spherical and/or platelet-shaped particle geometries. 
     
     
       9. The method according to  claim 1 , wherein an aqueous composition is used, which has a viscosity between 150 mPas and 2500 mPas. 
     
     
       10. The method according to  claim 1 , wherein the aqueous composition is applied to the substrate such that an area-related dry mass between 1 g/m 2  and 20 g/m 2  arises, and/or that the aqueous composition is applied to the substrate such that the layer has a wet film thickness between 1 μm and 1000 μm. 
     
     
       11. The method according to  claim 1 , wherein the aqueous composition is applied to the substrate by an equalizing coating method and/or by a contour coating method. 
     
     
       12. The method according to  claim 1 , wherein the aqueous composition is applied to the substrate at a temperature between 30° C. and 85° C. 
     
     
       13. The method according to  claim 1 , wherein the coated substrate is dried in step c) by infrared irradiation and/or by convection and/or under UV irradiation and/or that the coated substrate is dried up to a residual humidity between 3% by wt. and 12% by wt. 
     
     
       14. The method according to  claim 1 , wherein in step a), a substrate is provided, which includes a base material, the outer side of which is provided with a conditioning layer and/or a cover layer. 
     
     
       15. The method according to  claim 1 , wherein the substrate is coated with a further aqueous composition after step c), wherein the further aqueous composition includes at least polyvinyl alcohol and/or a polyvinyl alcohol copolymer and is free of cross-linking agents.